Process for softening vegetable fibers



Patented May 21, 1929.

UNITED STATES 1,114,459 PATENT OFFICE.

SIDNEY D. -WELLS, OF QUINCY, ILLINOIS, ASSIGNOR '10 PAPERIMILL LABORATORIES,

INC., 01' QUINCY, ILLINOIS, A CORPORATION OF ILLINOIS.

PROCESS FOR SOF'I'ENING VEGETABLE ,FIBERS.

in; Drawing.

This invention relates to processes for softening vegetable fibrous material, such as wood, cereal straws, and grasses, whereby a remarkably fin'e product may be obtained by the use of relatively inexpensive chemicals.

The invention includes the feature of relying on sodium carbonate to effect the softening action, as contrasted to a pulping action, all causticizing and dissolving action being avoided.

In my application for patent, Serial 119,471, filed June 29, 1926, now Patent-No.

1,626,171, April 26, 1927, entitled Process for cooking ve etable fiber is described an improvement 1n softening vegetable fibrous materials by the use of sodium carbonate and sulphur and without causticizing the sodium material. The present invention constitutes an improvement over that process of Serial 119,471 in that the sodium carbonate and sulphur are respectively substituted by the materials of spent cooking liquor known, as black-liquor, remaining after fibrous material has been pulped, as contrasted to softened, in the soda process or sulphate process. The liquor, as such, may be used and prior to and dispensing with the refining of the recoverable soda and sulphur content or it may be concentrated and burned andthe ash used in subsequently prepared solution. In either case causticizing is avoided.

Heretofore, in the manufacture of paper pulp. from vegetable fibrous material such as wood and straw, sodium hydroxide has been freque'ntl used either alone or in the presence of ot er sodium compounds, such as sodium carbonate, sodium sulphide, sodium sulphite, or sodium sulphate. The sodium hydroxide has been usually relied u on as the major pulping agent, and the ot er compounds are either present as unavoidable companions from the recovery process or on accountof their power to protect the cellulose from the drastic solvent and hydrolytic action of the h droxidel In the recovery of the digestors alon Application filed September 25, 1926. Serial No. 137,819.

the sodium carbonate is converted to sodium hydroxide by means of calcium hydroxide before use in the cooking operation. This conversion or causticizing step is obviated in the present invention.

vIt has now been found that where only the softening of the vegetable fibrous material is desired, it is not necessary to effect the conversion just mentioned, but soda, such as may be recovered from spent digesting liquors, can be used with whatever sulphur compounds occur, directly in the cooking operation. Where the products obtained may be of a deep brown color, the spent digesting liquor from the complete pulping operation on other material may be used, since much of the soda is in loose combination with weak organic acids or carbonic acid, and is capabio of considerable softening action. Spent softening liquor from the process disclosed herein or in my copending application Serial N 0. 119,471, in which there is provided initial materialconsisting of sodium carbon ate nd sulphur, would beof little use, however, on account of its greatl diminished powerto soften and reduce. t can be concentrated and incinerated and used the same as incinerated or smelted liquor from soda or. sulphate mills as a'source of sodium carbonate and sodium sulphur compounds in the preparation without causticizing of a softening solution suitable for the prepara- 100 ion of lighter colored pulp products as disclosed herein. If sodium sulphate be used to make up the loss in recovery or to even partially make it up, no additional sulphur is necessary for the present process. Other-' wise suiliclent sulphur should be added to with the solution of recoveredsodium sa ts and soda ash sufiicient to make up the losses to give a desired softening effect. 1

r In conducting the process, the cooking vessels, digestors. are charged with straw or other vegetable fibrous material in the usual manner, together with about sutlicient spent digesting liquor to furnish a strength equivalent to seven pounds of sodium carbonate, one pound of free sulphur, similar to the use of free sulphur as in my application Serial No. 119,471, and approximately one hundred and seventy pounds of water for every one hundred pounds of straw. The sodium carbonate and sulphur and water are of course not distinct as such since in the spent digesting liquor these materials are more or less in combination with each other and with other materials present. Accordingly the roportions given herein are specified merey to indicate'desired strength for treating a given amount of straw, and the qualities of the liquor must be either fairly well known or else it must be analyzed to determine its strength and composition. A cooking treatment of six hours is suflicient if at least five and one half hours of the treatment are conducted at a tem erature of 145 C. The action is conducts in closed vessels and at pressures greater than atmospheric. After digestion, the stock is dumped, washed and beaten according to established practice.

As an optional treating solution, it has been found that adequate softening may be obtained by using four parts of sodium carbonate and two parts of sodium sulphide for each one hundred parts of straw.

The above proportions relate to parts by weight.

Not only may sodium carbonate and sodium sulphide obtained in the recovery operation be used, but they can be purchased and used without recover 'When straw is use the steps are substantially the same as in common practice. \Vhen wood is used, avmechanical disintegration of the softened chips may be necessary, following the treatment described in m aplication for patent, Serial 49,461, file August 10, 19:25.

By using the spent digesting liquors described in the foregoing, it will be obvious that time and expense is saved by avoiding the known recovery processes which almost invariably had included causticizing where sodium hydroxide was to be obtained. It is of peculiar importance in the present invention in which the chief aim is to soften and pulping is to be avoided.

The present invention further differs from other processes in that sodium carbonate and sodium sulphide are proposed as cooking agents and with the exclusion of the usual sodium hydroxide which formerly has been used as the principal cooking agent. Sodiuin hydroxide is far too active an agent for the purpose of merely softening wood, straw, and similar fibrous material without completely dissolving the non-cellulose material.

It is interesting to observe that there are conditions, circumstances, in which the use of black liquor processes may be used, and this is wherethe. deep discoloration caused by their use would not be objectionable. It would be necessary to operate the process in conjunction with a plant engaged in making standard soda or sulphate pul in order to obtain a sqpply of suitable blacl; li uor. Attention is irected to the fact that t ie particular spent cooking liquor obtained from the softening operation disclosed in this application and in my application Serial 119,471, would not he effective because in it the soda is a stronger chemical combination and has lost its softening and reducing power, but this liquor, however, can be concentrated and burned just the same as in the soda and sulphate processes and thus the ash ma be used as a source of sodium carbonate an sodium sulphur compounds for making up a softening solution desirable where a product as light as possible in color is desired.

I claim 1. In the rocess of softenin vegetable from the soda or the sulphate fibrous material, the steps consisting of softening fibrous material by treating it without pulping it with the materials comprising the spent cooking liquors from pulping rocesses using sodium hydroxide and free rom the presence of more powerful chemicals, such materials containing sodium carbonate and being used without further refining and in the presence of sulphur.

2. In the process of softenin vegetable fibrous material, the steps consisting of soft ening vegetable fibrous material without pulping it by treating particles of such material in intermingled contact with the mate rials comprising the spent liquors from pulping processes and in which sodium carbonate and sodium sulphur mixtures have been used, and conducting such treatment to such an extent as to soften the particles, such materials containing sodium compounds and bein used with the fibrous materials to be soften and free from the presence of more powerful chemicals and without causticizing and in the presence of sulphur.

3. In the process of softening ve etable fibrous material, the steps consisting o treat ing particles of such material in intermingled contact with the sodium carbonate compounds recovered from pulping processes in which sodium carbonate and sodium sulphur mixtures have been used, and conducting such treatment to such an extent as to soften the particles, such sodium carbonate compounds being used with the fibrous materials to be softened and without causticizing.

4. In the process of softening ve etable fibrous material, the steps consisting o treating particles of such material in intermingled contact with a solution containing sodium carbonate recovered from pulping processes in which sodium carbonate and'sodium sulphur mixtures have been used, and conducting such treatment to such an extent to soften the particles, and using such solutions with the fibrous material to be softened in amounts of solution sufficient to furnish seven parts of sodium carbonate, one part of sulphur and one hundred and seventy parts of water for each one hundred parts of fiber, by weight.

5. In the process of softening vegetable fibrous material, the step consisting of treating particles of such material in intermingled contact with the sodium carbonate solutions recovered from pulping processes in which sodium carbonate and sodium sulphur mixtures have been used, and conducting such treatment to such an extent as to soften the particles, and using such solutions with the fibrous material to be softened in amounts of solution sufiicient to provide four parts of soduim carbonate and two parts of sodium sulphide for each one hundred parts of fiber.

6., In the process of softemng vegetable fibrous material, the step consisting of treating such fibrous material with a mixture of sodium carbonate and sodium sulphide, said treatment being conducted sufliciently long so as to soften the particles of such fibrous material.

7. In the process of softening vegetable fibrous material, the step consisting of treating such fibrous material with a mixture of sodium carbonate and sodium sulphide in solution, and conducting such treatmentto such an'extent as to soften the fibrous material, and using such solution in amounts sulficient to furnish seven parts of sodium carbonate, one part of sodium sulphide, and one hundred and seventy parts of Water for each one hundred parts of fibrous material, by weight. 7

8. In the process of softenin vegetable fibrous material, the steps consistmg of softening fibrous material by treating it Without pulping it with the materials comprising the spent cooking liquor from pulping processes and known as black liquor and free from the presence of more powerful chemicals and used without further refining'and in the presence of sulphur.

In testimony whereof I aflix my signature.

SIDNEY'D. WELLS. 

